1. Field of the Invention
The present invention relates generally to a color photographic material having improved color reproduction characteristics and, more particularly the invention relates to a color photographic material which provides excellent and faithful color reproduction by using the interlayer color correction couplers in an improved manner.
2. Description of the Prior Art
A multilayer color photographic material is usually composed of a support having thereon a photosensitive layer unit which is mainly sensitive to blue light (light of a wave length shorter than substantially about 500 nm.) and which contains a yellow coupler, a photosensitive emulsion layer unit which is mainly sensitive to green light (light of a wave length in a range of substantially from about 500 to about 600 nm) and which contains a magenta coupler, and a photosensitive emulsion layer which is mainly sensitive to red light (light of wave length longer than substantially about 590 nm) and which contains a cyan coupler. Each of these photosensitive emulsion layer units independently must fulfill its own function of specific color reproduction and for the purpose, intermediate layers, a light filter layer containing an ultraviolet absorber, an anti-halation layer, and a protective layer are formed additionally in the multilayer color photographic material. Also, each of the photosensitive emulsion layer units contains, independent of each other, a silver halide photosensitive emulsion having a spectral sensitivity of an appropriate distribution in a proper and specific wave length region and a coupler capable of providing a color image having appropriate spectral absorption characteristics. However, color photographic materials produced at present have various deficiencies.
A first deficiency in color reproduction is in the spectral absorption characteristics of the colored dye image obtained from the coupler used, that is, in that the colored dye image obtained has insufficient absorption in the specific wave length region and in addition has undesired absorptions in other wave length regions. Such a deficiency results in narrowing the color reproduction region and difference in color and reduction in color saturation.
A second deficiency is that the development of a specific photosensitive emulsion layer induces the coupling of a coupler in an adjacent photosensitive emulsion layer. This deficiency causes color mixing and, in particular, reduces color saturation.
A third deficiency is that the sensitizing dye used for the spectral sensitization of a specific photosensitive emulsion layer diffuses into an adjacent photosensitive emulsion layer to sensitize the adjacent emulsion layer and result in an improper spectral sensitization distribution.
Approaches toward improving these deficiencies have involved the provision of, for instance, intermediate layers and a filter layer and further the incorporation of a reducing compound, a hydroquinone derivative, a phenol derivative, an ascorbic acid derivative, a scavenger for the oxidation product of an aromatic primary amino color developing agent, a colorless coupling compound, a coupler forming a diffusible dye, a diffusion preventing agent for the sensitizing dye and coupler, fine silver halide grains, a clay such as colloidal silica and hematite, an anionic or nonionic or cationic surface active agent, a cationic hydrophilic synthetic polymer, a hydroquinone derivative hydrophilic synthetic polymer, and a polymer latex in such auxiliary layers. However, such improvements have not sufficed.
Another manner of improving the occurence of color mixing is in the introduction of photographic elements affirmatively possessing a "color correction" function. One technique is the use of a colored coupler equipped with an automatic masking function. These techniques are described in, for instance, U.S. Pat. Nos. 4,163,670, 2,455,170; 2,449,966; 2,600,788; 2,428,054; 3,148,062; and 2,983,608, British Pat. No. 1,044,778. However, these processes as described in the above patent art have the defect that the non-exposed portions are strongly colored. Therefore, colored couplers such as those disclosed above have not been used for color photographic positive materials and in addition when these colored couplers are used for color photographic negative materials, a long period of time is required for exposing the photographic materials at printing, which results in reducing the efficiency of printing work. Also, the use of such colored couplers tends to increase the formation of fogs, which results in reducing the granularity of the dye images.
A second technique is a process using the so-called "DIR coupler", or "development inhibitor-releasing coupler". The DIR coupler is defined in C. R. Barr, J. R. Thirtle, and P. W. Vittum, Photographic Science and Engineering, Vol. 13, 74N, 80(1969), bid., 214-217(1969), and U.S. Pat. No. 3,227,554. It is generally known that the DIR coupler provides an interlayer effect but the coupler has the disadvantages that the development is delayed, the gradation (gamma) is reduced, the maximum coloring density (D.sub.max) is reduced, and the effective sensitivity is also reduced. It can be said that the improvement of these disadvantages is a technical theme of color reproduction.
A third technique is a process using a substantially fogged silver halide emulsion or a direct positive silver halide emulsion in an intermediate layer. In addition, a process using a coupler together with the aforesaid silver halide emulsion, a process using an internal fogged type silver halide emulsion or an internal latent image type silver halide emulsion, and a process utilizing a Luckey effect are known. However, the use of such silver halide emulsions is accompanied by a reduction in sharpness caused by the scattering of exposure light by the silver halide grains, the difficulty in controlling the photographic characteristics of the emulsion itself, and also photographic side reactions.
A fourth technique is a process of controlling the composition of the silver halide emulsion itself used in each photosensitive emulsion unit, a process of controlling the inter-layer distribution of development accelerator, or a process of controlling the inter-layer distribution of a development inhibitor.
However, the color correction effects by the proposed processes are insufficient.
In another approach an element included in a development process is provided but the color correction effect by such an element is still insufficient.
As a process of improving the deficiency in color reproduction due to the insufficient absorptions in specific wave length regions by dye images from couplers used, a process in which a mixture of two or more couplers which form dye images having different colors as described in, for instance, the specification of Japanese Patent Publication No. 391/1965, is used.
However, since conventional couplers have, as mentioned above, undesired absorptions, the formation of "color mixing", increases on the contrary and thus by the proposed process color reproduction in a specific color may be improved but desirable excellent color reproduction is not obtained for all colors of interest, such as red, green, yellow, and intermediate colors.
It is also known that the photosensitive characteristics of a green-sensitive emulsion layer unit and a red-sensitive emulsion layer unit, in particular the photosensitive characteristics of a green-sensitive emulsion layer unit of the photosensitive emulsion layer units of a multilayer color photographic material and the colors of the dye images formed therefrom have the greatest influence on color reproduction. Also, various interlayer color correction uncolored couplers and so-called "DIR couplers" are known as described in, for instance, U.S. Pat. Nos. 3,006,759; 3,227,554; 3,632,345; 3,622,328; 3,617,291; 3,632,373; 3,642,485; 3,649,285; and 3,701,783 and U.S. Pat. Application Ser. No. 454,525, filed Mar. 25, 1974 now U.S. Pat. No. 3,933,500 now U.S. Pat. No. Re. 29,379.
Of the compounds described in the patent art described immediately above, the interlayer color correction uncolored couplers and the DIR couplers each having a pyrazolone nucleus have large defects for practical uses. For instance, a first defect is that the industrial production of such compounds is not easy. Thus, the cost of the compounds increases and also it is difficult to obtain those compounds at sufficiently high and constant quality. A second defect is that the interlayer color correction pyrazolone coupler and the DIR pyrazolone coupler each having a sufficiently high coupling reactivity to a color developer are chemically unstable. This results in desensitization of the silver halide emulsion containing this coupler, delay in the progress of development, and tendency to form stain.